On Tue, Apr 15, 2014 at 06:34:03PM -0600, Doug Royer wrote: > Yahoo does not seem to require DMARK. Simply use one of the other two > options. I use SPF for my domains, and it makes it through their systems > just fine. You seem to be confused about what the problem is. It's not that Yahoo is requiring DMARK. The problem is that Yahoo is requesting that *other* mailers reject mail if the From field is not aligned with the Sender, and the From field is from yahoo.com. This means that if a bob@xxxxxxxxx sends a message to a list which includes alice@xxxxxxxxxxx, and the mailing list server keeps the from field as "bob@xxxxxxxxx", and sends the message to all of the mailing list recipients, which includes alice@xxxxxxxxxxx, the following things will happen: a) hotmail.com will compare the sender address (authenticated with SPF) with the from address (authenticated by DKIM), see that they are different, and since yahoo.com has a DEMARK p=reject, hotmail.com will bounce the mail. b) this means alice@xxxxxxxxxxx will never see bob@xxxxxxxxx's mail c) since the mailing list server receives a bounce from hotmail.com, if there are enough attempts from yahoo.com users to send mail to the mailing list, the number of bounces will cause the mailing list server to suspend or remove alice@xxxxxxxxxxx from the mailing list. If we munge the from field from bob@xxxxxxxxx to bob@xxxxxxxxx.INVALID, then hotmail.com will not bounce the mailing list mail. This means Alice will see Bob's message, and Alice will not be in danger of getting suspended or dropped from the mailing list. Alternatively, the mailing list server could determine the Bob is sending his mail from a domain that has a DEMARK p=reject policy, and simply bounce the mail back to Bob right away, instead of sending it to the mailing list recipients. That way, Bob's can get pursuaded to use another mail provider, and Alice doesn't have to worry about getting suspended from the mailing list. Do you have another suggestion about what the mailing list server is supposed to do? - Ted